A couple of points with regards the UK from my perspective
The UK DTA states that income from property may be taxed in the country the property is located in so for those renting out property in the UK there should be no Thai tax liability. "Income from immovable property may be taxed in the Contracting State in which such property is situated."
An official guidance update from the Thai revenue department dated 6 October 2023 ( Revenue Department orders No. P.161/2023) states
"assessable income due to work duties or activities conducted abroad or because of assets located abroad" would remove any liability for income from the UK State Pension as the State Pension could in no way be described as income from an asset abroad.
