Linda, for your travel itinerary and if this is your first time in Thailand I don't think you would need a METV, as the first entry could be done on Visa Exempt and the 2nd one either SETV from Malaysia or another Visa Exempt and extension inside Thailand. Anyway, if you still want to apply for the METV in Madrid, you need to go there in person or send the document via mail (no appointment needed) hand over all the documents and in 2 business days you can pick up your passport with the Visa if granted, now its 175€ for this Visa. If you have permanent residence in Spain you should have a NIE which will serve you to confirm that on the Embassy and being able to apply, a legalised copy will be needed. They also request for a bank statement showing at least 5000€, some proof of your job (payslip, contract, etc.), hotel bookings for the whole stay and at least 2 flight tickets in/out Thailand. If you are not employed in Spain, but you are retired you should show a letter from your pension plan stating how much you get. I have never heard about the guarantor in Spain, so this should not worry you much.