Exploring possibility of bringing my Thai nephew over to the UK to attend primary school in the UK and am looking firstly at a 1 month visit by him on a tourist visa later this year just to see if he can actually settle in the UK without his parents. If he can't settle in UK then no problem he goes back to Thailand and carries on as he was. If after visiting he still wants to come to the UK to study has anyone on the forum had experience of the visa application and what type is required to enable him to come and study in the UK?

Thanks

To study at a school in the UK he will need a Tier 4 (Child) student visa.

Note that this will only allow him to attend an independent, fee paying school which is on the register of licensed Tier 4 sponsors and he must have an unconditional offer of a place at that school when he applies for the visa.

He will not be able to attend a state school unless he comes to the UK to settle.

As you say he is currently living in Thailand with his parents, the chances of him getting a settlement visa are zero.