The train journey from Singapore to Kuala Lumpur, Penang, southern Thailand and Bangkok is about 1,920 km or 1,234 miles, an epic adventure journey, incredibly cheap plus really quite comfortable and civilized. You can move in either direction, southbound or northbound it is up to you. This entire journey costs one as little as $75 or £54. Of course, you do not have to do the whole trip – the cabin is great especially for travel between the towns of Singapore & KL, or even between KL and Penang.
There’s no such a thing as Singapore to Bangkok tickets, you simply purchase a ticket for a specific train you wish to take. You may book any train operating between any two train stations, each ticket comes normally with reserved seats or sleeping berths on a specific train and date. So look at all the timetables given and create a train journey which suits you, stopping off in every place you wish to see. Later book each train singly as well advised how to purchase tickets section.
Trains in Malaysia and Thailand run on meter gauge tracks, narrower than the European standard gauges, much of this single track, built and curvaceous in the 19th and early 20th centuries. However, large parts of the line in the city of Malaysia are currently being modernized for the upcoming ETS electric train cabins to run at close to 150 km/h (100 mph) leaving them probably the very fastest meter gauge trains around in the world. In Malaysia, you will often see big sections of the old colonial one-track line and any new double-track electrified lines side by side and just some yards from one another.
The line’s connection in Singapore has suffered greatly in the past few years. Until 2010, trains left from several wonderfully faded grandeur located in Singapore’s art deco train station, built in 1931. Sadly, the Singapore national government took over this from Malaysians and later closed it down, therefor trains to KL and the north currently leaves from Johor Bahru (Sentral) Station just up north of the main causeway into Malaysia. However, shuttle trains operate from Woodlands Checkpoint located south of the main causeway, or one can take frequent local buses all the way right from central Singapore region to JB Sentral station. The options for changing to or from Singapore downtown are explained here,
If you were currently in a hurry one travel from Bangkok to Singapore in less than 2 days using train cabins 20 overnight departing from JB Sentral stations to Hat Yai station then train 180 or train 38 overnight from any place in Hat Yai to Bangkok, however I’d recommend stopping at Kuala Lumpur or Penang as both are fascinating cities.
So perhaps take a morning train from Singapore to Malaysia, or the very time-effective overnight sleepers (train 24). Stopover in KL shortly for a day or more, then take any of the ETS trains you prefer from KL to Butterworth, that is the train station for a ferry shuttle to regions of Penang. After one day or more exploring Penang, do take comfy sleepers on train 38, the International recognized Express leaving Butterworth town at lunchtime and getting to Bangkok the next morning. One could stop in southern Thailand and if you like, it is entirely up to you.