At risk of further feeling the wrath of Davidfl, with off-topicness, but at least aboot riding in Thailand...
It surprises me that Tony posted up the response he did, since it seems that our Merican brothers more typically lean towards "It's the law, so must be obeyed"...
I don't obey any law, just because it is the law... I obey the law because it meets my own moral standards (i.e. not negatively impacting on others), or because the risk of not obeying the law is too great...
Here in Australia, speeding by more than 45 over is $2,154.00 and 6 months license cancellation... I rarely do more than 45 over, but will comfortably do less than 45 over, because the risk isn't so great...
I wouldn't ride without a license, because the penalty is huge... but in Thailand, then penalty (from a law enforcement point of view isn't huge)...
For the OP, he needs to make a decision about whether;
The penalty is acceptable (especially the possible massive cost if there is an accident - no insurance)...
It passes the morals test (aside from not having a license, is riding a bike they have no experience with, putting others at unacceptable risk)...
I personally recommend that people don't ride a bike they aren't licensed for because, we all know how often inexperienced riders crash in Thailand, and that the medical costs without travel insurance coverage can be huge... but that is up to the OP to decide for himself....
The great thing about Thailand is that you can make an educated decision about that... In Australia, I reckon you would be MAD to ride without a licence, mainly because the cost of vehicle repair/medical costs are so huge (the fine is only $792)...