Thailand sense of national identity is by its history as

Thailand sense of national identity is helped by its history as free nation.

Explanation:

Thailand is the only country in the region of South East Asia which was never a colony of the Britishers. Almost all the neighbors of Thailand were colonies of Britain but never Thailand. Thai means free which was always independent and never under the rule or authority of any power.

Because of this reason, it is also known as the land of the free which were uncolonised and this has helped develop a feeling of national identity among the people who are living there or national identity in the past also.