My friend and I are going around the world starting June 2009 for just under 7 months.
Our route, budget and durations are:
Thailand (overland Singapore) - 1 month (600 pounds)
A couple of observations regarding this leg of your trip.
I assume you're flying into Singapore and then making your way overland, probably by train through Malaysia to Thailand. If that's indeed the case, you'll only be permitted to stay for 15 days under the terms of the Visa Waiver program that most countries have signed up to. That's because you're entering the country via a land border.
If you wish to stay for a month and still enter the country via a land border, you'll have to apply for a Tourist Visa which enables you to stay for up to 60 days. A single entree Tourist Visa costs 1000 Baht which is about £19 and must be applied for before you enter the country. Details on how to obtain a Tourist Visa on the MFA site here: Thai Visa Applications
Next point is the insurgency which is operating in the border region between Malaysia and Thailand at Sungai Kolok. This is where the train crosses from Malaysia into Thailand. At the beginning of this month, gunmen attacked the train killing two railway workers whereby the service was suspended for 13 days. Two border policemen were killed only yesterday in the same area. These are not isolated incidents and more than 3,500 people have been killed in separatist violence in southern Thailand over the past five years.
So your best bet would be to fly from Singapore to Phuket, or to Bangkok and then plan your vacation in Thailand from that standpoint.
Then there's the amount you propose to live on for a month. £1 = 52 Baht at the moment. So you've only got 31,000 Baht to play with. If you're going to do couchsurfing, then all well and good, but it will require some planning and there aren't that many places available around the main tourist hotspots. If you have to stay in guesthouses, then allow 600 Baht a night which leaves you only 433 Baht for food and drink. Thailand is cheap and you can live on that, but you'll have to forget partying because you won't have enough left over for that as well I don't think.
Here's a map of the rail network which includes links to fares, timetable etc., and might help you find your way around: Thai State Railways
Anyway, good luck!