So here's an update. I've made it to the next step in the application process. First there was a 30 minute Skype interview with representatives from the US embassy in Thailand, the IIE in the US, and also a Thai citizen Fulbright Alum. The interview was partly in English and partly in Thai. A few days later I was contacted again and told that there would be a follow-up language evaluation in the form of a Thai reading and writing test. That involved reading a short article in Thai, summarizing it in English, and then writing a 1 page commentary on the subject in Thai that needed to be completed in three hours. Suffice to say, they are very serious about host country language fluency for this program! In the interview they mentioned one of the possible job duties as a special assistant in the government ministry could involve policy speech writing in the host language!
As for the questions on my background, I studied in Thailand for seven months as an undergraduate and have been back multiple time since then for travel and work. Most recently I've been working on a dual Master's degree in Urban Planning and Southeast Asian Studies. I would say my language skills are high intermediate.