@Sahnna **************
You have received some good advice here, but also some half-witted advice, you can do two visa-exempt entries by a land border per calendar year,
and officially claimed “unlimited” visa-exempt entries by air, which is NOT really true, as you can get pulled aside and questioned upon the third attempt – (you will need to show 20,000.- THB in THB or another major currency, proof of accommodation and proof of onward travel within 30 days)
You will be able to arrive visa-exempt, get 30 days stamped, you can extend them for 1900.-THB on Immigration for 30 more days (some immigrations will want to see your TM30 registration which will not be a problem since hotels register their guests per online TM30)
And you will be able to fly to Bali, enjoy a holiday, return to Thailand by air (you might get asked to show a proof of onward travel within the 30 days you will get stamped in visa-exempt, by the airline, though)
and get a second visa-exempt entry for 30 days.
And after this, just stick to what I advised, in case you wish to extend for further 30 days, keep alert and be prepared to have a "plan B" just in case the
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rule will be imposed and the extension rejected.