Japan says Thai bullet train to cost nearly $13bn
https://asia.nikkei.com/Politics-Economy/Economy/Japan-says-Thai-bullet-train-to-cost-nearly-13bn?utm_source=paid.outbrain.com&utm_campaign=BA%20JPN&utm_medium=referral
The most important thing is speed Thai government requires and cost they can pay. Japan seems to have offered just muximum speed. But, considering the construction cost increases proportional to required speed, it would be better to ask Thai government how much they can pay and how fastly the new train should run.