How much money should I show for a 30-day visa exemption in Thailand?

There is no law in Thailand which dictates that travellers must have baht in cash in their wallets. It is pure whimsy at the discretion of border officials. If you're happy with letting your life be dictated by the whimsy of people in uniforms then by all means do as others suggest in this group. If not, then perhaps visit a different country for your holiday. Some feel that life's too short to waste on appeasing power tripping pettiness.

20,000+

We all hear of many people not being checked and stories of people who do get checked

The application for 90 day non o is the same amount as tourist visa or 30 day exemption

Was told arrive with £400 cash but have never been checked on any entries but that’s not to say it won’t happen in the future

Recently applications have not been processed until 3 month bank statements have been provided also with application

Must show £1500 per month

But the U.K. embassy said it was fine if I could show money going in and a total of £1500 in the bank at time of application

(So double check with your embassy what they require as financial proof I believe Australia applicants are different to U.K. applicants)

As my experience, it depends on immigration officers. Some officers ask you some not. Mostly they didnt ask. You might show 25.000 baht.

Also if you think you may extend you exempt stamp you'll need to do a TM30

And change your status which shows you as living in thailand they do check facebook

And also proof of hotel booking, and a return flight or flight out of thailand.

You mean a visa exempt? You might get asked when arriving to show baht by an immigration officer when arriving.