I will try to provide a short run-down, in alphabetical order, on what you can expect in some Asian countries.

CAMBODIA
You won't find a Cambodian girl who will enter a sexual relationship with a foreigner because she is interested in sex, and not even in love. The interest is almost always in money. This goes for prostitutes as well as for those who become the wives, or sort-of wives, of foreigners. Plenty of foreigners in the country, many affiliated with NGOs. There are also a large number of Cambodians who have fled during war times to Western countries, and who have since returned (and often are subtly anti-Western).

CHINA
Ordinary Chinese girls will not speak English. However, female students in a language program, or young women who are on a career course often find it helpful and appropriate to have a foreign boyfriend. In local discos, foreign men are usually considered attractions. You can also find women (mid-twenties and older, not prostitutes) who will approach on their own a foreign man whom they consider attractive. Outside of the main urban centers, foreigners are rare (and all the more considered an attraction).

INDONESIA
This was a very charming country until only a year or two ago, though it was even more charming some 10 years ago. However, there have been developments which have turned this country into a less-than-ideal destination. First, anti-Western sentiment has been on a steady rise in the post-Suharto years. Law enforcement against so-called social ills (including sexual relationships outside Islamic norms) has become rather strict. Young Indonesian women may still be attracted to Western foreigners, but the emphasis is now more on marriage than used to be the case.

JAPAN
Both white and black men are considered better, and better-endowed, lovers than Japanese men. Japanese women interested in love affairs with foreign men may take the lead in arranging the relationship.

MALAYSIA
Young women of all three ethnicities, Malay, Chinese, and Indian are genuinely attracted to Western men. However, don't expect any intimacy with Malay girls before marriage. The punishment for being alone in a room with a Malay woman is either on-the-spot marriage or prison. The marriage option is open even for those men who are married already. For non-Malay girls (Chinese, Indian), promiscuity and even prostitution are legal.

PHILIPPINES
You can definitely have love relationships with Filipinas, and the fact that English is widely spoken, indeed, facilitates such love relationships. On the other hand, because English is so widely spoken, you cannot as easily distinguish yourself by learning the local language. If you speak Chinese in China, Indonesian in Indonesia, or even Thai in Thailand, your options are much better than those available to newcomers. There is no such distinction in the Philippines because most people anyway speak English.

THAILAND
A principal social concept in Thailand is that daughters give money to their parents. In the past, many rural girls achieved this by becoming prostitutes. I assume that much fewer girls in Thailand now become prostitutes. But the imperative that daughters provide support for their parents is still strong. If they speak enough Thai to communicate what they want, foreigners can marry local girls, provided they pay dowry of 5000 dollars or more. There is no necessity to register a marriage (thus officially, there is no marriage), but even the Thai side will normally not expect the marriage to last forever.