score:2
No adapter needed. Your flat blade plugs will fit just fine in 98% of the outlets
Upvote:2
According to Wikipedia, Thailand has types A, B, and C plugs while the USA has A and B. A is the two-prong no-grounding plug you're familiar with and B is the three-prong grounded plug you're familiar with also. (There are pictures down the side of the huge table on that page.) C is the two-prong Euro style plug, so if that was all that was available in a place you would need an adapter, but it seems likely that hotels and such will have those adapters if needed, since the other kinds of plug are also in use in the country.
To be on the totally safe side, take an adapter to convert two-prong A (your electronics) to two-prong C (possibly the plugs in some rooms.) You may never use it though. To live a little more dangerously, buy one of those in Thailand if and when you come to need it.