Do I need to apply for a new TM30 after leaving and re-entering Thailand?

TM30 should be filed within 24 hours of taking up residence in a private house or hotel etc. The property owner is responsible for doing it and it has no expiry date. Some immigration Offices require a new tm30 to be filed with them on returning from an in country trip while some don't. It can be done on line.

The 90 day report tm47 has an expiry date exactly 90 days from the date you entered Thailand or received a visa extension. If you leave the country within the 90 days it re sets when you come back. It can also be done on line but will be rejected if your tm30 is not up to date.

I hope that explains it. For the finer details ask at your local immigration office.

There's no expiry date on a TM30. What are you talking about?

You're meant to get a new one every time you come back into Thailand

Every time you leave and return you have to put in your TM30

Also in Bangkok you have to show up for your 90 day report on the first one after you return to country…after that you can do it online

This is every-time

TM30s don't have a real validity date, there is a proposed length of stay at the accomodation when filed and that might be the date that you see. Every valid tm30 is invalidated by your next filed TM30

In Jomtien with DTV you need to make new TM30

The policy varies by immigration office, you need to ask them what their policy is

I'm in Bangkok and get a new one every time I come back

If u leave thailand and comeback dont need to fill tm30 just fill between 85-90 days within fresh entry

Depends on what office

It can depend on which office if you are returning to same address. For example in Jomtien no need to update TM30 but in Chiang Mai it must be done - "This is Thailand" :-)

Yes