Hi, thanks Lunthom. I just logged on to post this news also. But not only have you beaten me to it, there is already a discussion about it. Amazing.
Supposedly English isn't ready yet, so for a short time, the world's Thai speakers will have an advantage booking their tickets on this system

, but no doubt an English version will soon arrive.
Here is the Bangkok Post article:
By: BangkokPost.com
Published: 28/01/2009 at 02:53 PM
People will be able to buy railway tickets online, starting Sunday, according to State Railway of Thailand (SRT) governor Yutthana Thapcharoen.
He said the online ticketing system will initially be tested for 16 routes for six months, and believed it can help increase the number of railway passengers by 30 per cent.
Some of the routes include Bangkok-Chiang Mai, Bangkok-Ubon Ratchathani, Bangkok-Trang, Bangkok-Nakhon Si Thammarat, Bangkok- Sungai Kolok, and Bangkok-Butterworth.
The SRT is also experimenting with using smart cards to buy railway tickets in convenience stores, Mr Yutthana said.
Starting Sunday, people can buy railway tickets online by clicking on the ‘E-Star’ banner on the SRT website at www.railway.co.th.