You may well find the senior monks not very conversant in english, but you should find younger monks who speak english fairly well, though if you have trouble understanding foreign accents you may not have much luck. Any services are probably going to be prayers in pali and talking in native language, in this case Thai. After prayers you may be able to interview the monks and someone at the temple might be able to act as translator for you.
18 years ago I made one of the most important decisions of my life and entered a local Cambodian Buddhist Temple as a temple boy and, for only 3 weeks, an actual Therevada Buddhist monk. I am not a scholar, great meditator, or authority on Buddhism, but Buddhism is something I love from the Bottom of my heart. It has taught me sobriety, morality, peace, and very importantly that my suffering is optional, and doesn't have to run my life. I hope to give back what little I can to the Buddhist community that has so generously given me so much, sincerely former monk John