Pure Thailand - from north to south with a short visit to Cambodia

Hi all - I will be in Bangkok from 08.12 and fly back on 07.01 from Krabi. Planned is a few days Bangkok, Angkor Wat in Cambodia back to Bangkok then further to the north Ayutthaya (to save time, by train) Chiang Mai and Chiang Rai (should be the last station for me in the north, because from Chiang Rai the flights are cheaper to the south) South Thailand: Koah Sok National Park , a few islands and on 6 latest Krabi, where on 07.01 goes the return flight. Briefly about me: I am 34 and come from Cologne - am uncomplicated and willing to compromise. I would like to get to know the country and the people. From time to time a party (not exaggerated) or a few days relax should also be. I have low requirements for my accommodation (clean, good location) because I do not want to stay long in the hotel anyway. Now and then a little more luxury would be nice, but not a must. would be happy if someone has the same part / plans ;) and you can discover some together. Greetings Marta The cost should be around 1000€ without flight to Thailand - of course the bit depends on the chosen flights and accommodations