This is easier than most people think, and it also depends less on personal characteristics than most people assume.
First, you have to choose a location that is appropriate. The Philippines is suitable wherever you go, as long as you speak English. Another option, if you don't speak a local language, is Kuala Lumpur. The rest of Malaysia is more difficult.
In spite of its long-standing reputation as a sex destination, Thailand is rather difficult for girlfriend relationships. Thailand, of course, has an excellent brothel infrastructure, but sex with prostitutes is not considered on this site.
While in Pattaya and Phuket, love-based sexual relationships with foreigners are common, Thailand overall is less than ideal for foreign men because Thai women typically consider Thai men superior to foreign men, and the social status of a Thai women who marries a foreigner actually falls, while in Malay countries (Malaysia, Indonesia, the Philippines) as well as Cambodia, the social status of a local woman rises if she marries a foreigner.
Vietnam is a special case because you will likely be hassled big time by the local police. I know foreigners who live in the Vietnamese communities in Phnom Penh and Sihanoukville, so if you are dead set on having a Vietnamese girlfriend, your best option will be in Cambodia.
Be aware that both Vietnamese and Khmer are very difficult languages, which will be a handicap for many years.
On the other hand, if you speak Indonesian (and this is probably the easiest language on earth), no other destination beats Indonesia for love relationships with local women.
As I have indicated in another article (in the non-member section), to choose the right destination for your sexual adventures is the most important decision, I'd even say: of your whole life. To be at the best possible place enhances your prospects for an alpha male lifestyle by a factor not just of 5, but of 500.
However, to make proper use of the options that present themselves to you, you will still need an appropriate setting. You will need a house or an apartment, or, even better, you have two.
You can meet a local girl who may be very interested in a sexual relationship with a Western man, and who would be available for sexual adventures. But if you don't have a place where to go to, the sex part won't happen.
Non-prostitutes rightly won't visit you at a hotel room. Non-prostitutes rightly don't agree to a sexual relationship with a non-resident. The likelihood would be far too great that the man will disappear all of a sudden, leaving her with a broken heart and, possibly, with a broken hymen as well.
Therefore, my approach is that as long as I haven't rented a house or an apartment yet at a location, I don't waste much time hunting for prey.
I may do some test runs, though, simply to assess the potential of a location.
Renting houses is easy and cheap in Thailand, even in Bangkok. It's a bit more expensive in Manila, and the selection isn't quite as good. In provincial towns in the Philippines, you may have to look around for some time. Phnom Penh is considerably more expensive, as there isn't much available that would be suitable for foreigners. Kuala Lumpur and other Malaysian towns have a good selection of houses and flats for rent, but prices are at least double (and often triple) of those in Bangkok for a comparative place.
Jakarta can be rather difficult. Smaller houses are in neighborhoods that are extremely crowded and not suited for foreigners (especially if you need a certain degree of anonymity). Houses in areas that are not crowded are always rather large. Compared with other Southeast Asian countries, rent in Indonesia is cheap. In Jakarta, you can find a suitable house for 3,000 US dollars per year, and in provincial cities, the prices are half of that, or less.
The disadvantage of Indonesia is that rents are collected for one or two years ahead, all payable before one can move in. To pay some 6,000 US dollars up front may be a bit much of a commitment, especially if one doesn't hold a residence permit.
In all other Southeast Asian countries, rents are collected monthly.
Visa extensions are easy in Thailand, Cambodia, Malaysia, and the Philippines, and in each of the countries, one can stay for years by just extending or renewing a tourist visa.
This will not work in Indonesia. After three consecutive tourist visa visits, an additional visa may not be granted.
Residence permits for foreigners are expensive in Indonesia. To start from scratch, one will need 5,000 to 10,000 US dollars, and processing time may easily be half a year, as there is no way around setting up a company (or getting employment status in an existing one).
Though residence permits are difficult for Indonesia, the girls are worth the effort and expenses. And Indonesia is not in danger of getting spoiled by too large a number of foreign resident males, simply because of the costs associated with an extended stay.
Immigration matters are rather difficult for Burma and Vietnam, but both countries anyway are police states, and have little to offer in sexual adventures in the playboy category.
If you rent a house or apartment in Southeast Asia, security is a concern.
The safest country to live in is Singapore. For houses and apartments (or flats), it is also the most expensive one. Though many Singaporean girls are beautiful, Singapore is not economical for sexual adventures. Most foreigners living and working in Singapore end up with Indonesian girlfriends, but Indonesian girls in Singapore typically are sexually experienced and often of dubious background.
The next safest countries are Thailand and Malaysia. In Bangkok, Pattaya, or Phuket, a foreigner can rent a house in any neighborhood. It won't be unsafe, and one will not generate an uncomfortable level of attention. There isn't much incentive to rent a house in a provincial Thai city, because normal girls in provincial Thai cities are difficult prey.
To rent a house in Vietnam is a huge hassle, and there is no rationale for doing so.
Cambodia, especially Phnom Penh is the unsafest place to rent a house. You would be advised to employ your own security guards, but that may be no guarantee against being robbed by armed men. You may also suffer physical harm, even if you are cooperative. If you are unlucky, your security guard will work together with the robbers and be their informant.
You may also be held up if you drive your own car, and even when using a taxi at nighttime. The measures I usually recommend for anonymity can mostly not be applied in Cambodia. Not only may anything you own there (especially a car) be robbed. Possessing things also puts your life and health in danger. This hasn't changed in more than 10 years.
My two favorite countries, the Philippines and Indonesia, aren't as safe as Thailand, but they are still much safer than Cambodia.