You can either leave Thailand at the end of 60 days or apply for an extension of stay for 30 days.
There is no minimum amount of time you need to be out of Thailand for. If you can find flights that suit you can head straight back.
The house owner should file the TM30 for you. If that’s your gf then get her to sign up to the online system, which once registered only takes a couple of minutes to file.
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