Indeed. What an amazing coincidence that there are only a few ("32") confirmed cases in the entire country. The UK brings one guy back, from a population of 70M, and guess what, he has it. A not previously confirmed case.

From statistics, one would take the number of prisoners brought back and tested (?) divided by the number of prisoners brought back with covid-19, multiply by 70M (the population of Thailand), and estimate, what, 10M Thai cases? Unlikely based on empirical knowledge. Looked at the other way, if one said it was true that only one person in 2M in Thailand has covid-19 (32 out of 70M), then the chances of bringing back one person and that one person having covid-19 is of course, one in two million. Those kind of numbers are much stronger than the 1-in-20 or 1-in-1000 that a scientist might normally use to say "probably false" or "false".

TL;DR: Likely that there are a whole lot more than 32 cases in Thailand, and that the UK probably had bad luck as well, bringing someone back from an unreported cluster.