Phuket immigration requires and. Id card owner, copy housebook, first page and page with the info of the owner, signed in real, no photocopy signature, the rentalagreement and indeed a power of atternay if the landlord not register his custumer by himself
if you do your border run to Vientianne it wikk the last bordercrossing this year by land. I suppose you fly to siem rap, in tgat case you can do if after your return, if you cross the border with Cambodia by land, you need to appky for your non b before travelling
If you have at least 12 days left on your visa excemption, you can apply in the immigration office of the place where you live, for a non o in thailand. This allows you to stay 3 months. At the beginning of the 3rd month you can apply for a retirement extension of one year. One of the easiest extension here.