We are wondering how much Thai we would need to learn in order to make our trip more successful.

You might want to start off with a phrasebook on Thai language. This should include basic phrases like ordering food, getting accommodation and shopping etc...

Thai Phrasebook by Lonely Planet is good. It has sections on basic Thai grammar, Meeting people, Getting around and also includes a Thai-English and English-Thai mini dictionary. Quite handy and it should fit in your pouch nicely.

Unless you're going to non-tourist destination or rural places, there're bound to be someone who is able to speak English. Just relax and have fun.

- Yeows