The test done by Thai webmasters Association shows that Samart is the best internet provider in Thailand. The upload and download speed was about the same all the time. The Thai internet providers have long lived on big promises and little to show for. When you read on the adverting that they should give you for example 2 MB they only provide maybe 1 MB or less.
TTT or Max net delivered 78 % of of the speed they advertised
CS loxinfo delivered 69 % of of the speed they advertised
TOT delivered 68 % of of the speed they advertised
I-Net delivered 64 % of of the speed they advertised
CAT delivered 51 % of of the speed they advertised
You can read more about the speed test here