Increasing the legal speed limit would only result in stupid people killing people faster.
In the West we have patrol cars for monitoring and controlling drivers. If you're observed speeding, driving recklessly, or violating a safety law, you're pulled over to the side of the road and ticketed. If you're driving under the influence of alcohol (or drugs) you are arrested, incarcerated, and fined, with the possibility of also having your drivers license suspended or revoked.
There are no patrol cars monitoring drivers in Thailand, nor do the motorbike police enforce the laws. The exception being the totally random road blocks where donations are paid. Rarely, at least from what I've observed, do these roadblocks result in drivers being arrested, or, for that fact, forced to go to a police station to pay a ticket for their violation. The way traffic laws are currently being ignored by the Traffic Police, there is absolutely no motivation for those who continually break driving laws to stop doing so.
The Transportation Ministry ranks "Speeding" as the leading cause of accidents. After 20 years of driving in Thailand, I disagree with this, and rank "Reckless Driving" as the leading cause. Of all the road accidents I've witnessed, and there's been more than I care to count, almost all have been caused by reckless driving, including, but not limited to, improper lane usage, failing to yield the right of way, tailgating, failing to reduce speed on yellow warning lights, failing to stop at red lights, erratic breaking and acceleration (drunk), and the list goes on. This type of irresponsible driving is the source of most of the accidents.
The only way I know of to reduce these accidents caused mostly by ignorant people, is to have the police monitoring, controlling, and enforcing the laws. It doesn't matter รf you give them high-tech GPS systems, laser guided stun guns, or drone satellite surveillance, if the police are not expected to enforce the laws, the laws won't be followed.
Traffic Police are paid the same amount as trainee 7/11 clerks. If the Transportation Ministry was really serious about reducing accidents and road fatalities, you think they would increase Traffic Police salaries, and start recruiting and training a more professional and disciplined police force with higher expectations and closer monitoring.