What should I do after overstaying my visa in Thailand and planning to return soon?

probably

You can probably apply for a Tourist visa from Phnom Penh, rather than going back to SA. (Other countries also possible but PP most flexible.)

Your overstay shall be recorded and listed on thai immigration system I would most certainly get a paid tourist visa before returning to Thailand BUT that doesn't guarantee you return entry you will pay for the visa before visa is granted and your application can be refused and the money is not refunded if you do make it back upon check in at airport immigration you're entry will be answered by the IO whom sits in front of you and he or she also can refuse you entry if he or she doesn't like the way you brush your hair you may have wasted money on airfares it's not a guaranteed entry for anyone technically there no written law for entries by air but you can only get 2 extension and or border crossing in a calendar year Chokh di you may need it

More feeble excuses. Every over stayer just ruins it for the rest of us

Immigration officer on the day may see you as a risk after 23 days overstay and refuse you entry. No one can be 100% what the officer on the day will decide.

the rules are clear. the only missing info to answer the question is to know how many days overstay there were

I think it all depends on how long your overstay was?

Also depends on what Immigration records have been entered onto the computer regarding the overstay.(A criminal offence in Thailand).

And the discretion of the Immigration officer dealing with you upon your return?

Depends on your visa, entry and exit history. If you recently stayed longer in Thailand already, coming back so quickly might lead to being challenged at the border. An overstay stamp in your passport certainly won't be beneficial, then. Get a visa before you come back. That makes entry more likely - yet does not automatically guarantee it.

Just apply for a visa or come back in a 30 day visa exemption stamp which can be extended at your local immigration office for ฿1,900

Get a visa before you come back