For visa applications bank statements work however

at immigration entering Thailand needs to be cash. (IF the officer requests to see it)

You can only have 2 visa exempt entries by a land border each year. Each entry giving 30 days. Any more than 2 and you'll need a visa (tourist or other) or arrive back into Thailand by air (and probably not at southern airports - as they can be keen on proofs and also denying repeat visa exempt entries)

Yes, both German and UK citizens can get visa exempt entries.

I'm guessing you have UK passport, in that case (and if you have not arranged a visa prior to arrival) you would get a visa exempt entry, this allows 30 days. This can be extended in country by 30 days at thai immigration offices. To stay longer in Thailand you can then "border bounce", giving you another visa exempt entry for 30 days (again extendable by 30 days).

You can have only two visa exempt entries by land border per calendar year.

So:

Initial arrival plus extension

30 + 30 =60

Border bounce 2 times

2 x (30 + 30) = 120

Total 180 days.

(If you have perfect timing)

You should note your airline may require proof of travel out of Thailand within the first day period.

You may also need to show various proofs of cash, accommodation, and onward travel for each of the border bounces to the Thai immigration officer.

Some of the info in this link is years out of date,

- Suan Phlu closed for this type of service years ago . .

Any immigration office should / will sell you a reentry permit, also available at international airports.

A reentry permit will not pause the visa - (your remain date will not change). Obviously your return date must be before the current permission to remain date.

If at suvarnabhumi an additional 200 baht fee is charged.

.

The marriage would also need to be between M&F - Thailand does not (yet) recognize SS marriages, even if legally recognized in home country.

I'm sure Tod / other admins will correct if wrong - but I believe that to be the case. Will need to confirm with my friend's in same situation.

So your friend's spouse to be is on a non-0 or extension of stay based on being over 50.

If / when they are married then I believe that yes the other (younger <50) partner can 'ride' on the spouse's retirement visa / extension of stay.

Plus an extra 30 if you extend it at immigration inside Thailand.