first of all we don't address her so informal since her father is the current king. we address her as “Tul-kra-mom-ying Ubolratana” which is probably equal to Princess Ubolratana. her title (HRH) hasn't been restored since she moved back, and i personally i do not believe she'll ever get it back during the king's reign. she'll probably get it back when her brother or sister becomes king. Under the current palace law of succession (B.E. 2467) does allow woman to rule the country but she'll never be addressed as queen.
Constitution of Kingdom of Thailand – Chapter ll – The King
Section 23. In the case where the Throne becomes vacant and the King has already appointed His Heir to the Throne under the Palace Law on Succession, B.E. 2467, the Council of Ministers shall notify the President of the National Assembly. The President of the National Assembly shall convoke the National Assembly for the acknowledgement thereof, and the President of the National Assembly shall invite such Heir to ascend the Throne and proclaim such Heir King.
In the case where the Throne becomes vacant and the King has not appointed His Heir under paragraph one, the Privy Council shall submit the name of the Successor to the Throne under section 22 to the Council of Ministers for further submission to the National Assembly for approval. For this purpose, the name of a Princess may be submitted. Upon the approval of the National Assembly, the President of the National Assembly shall invite such Successor to ascend the Throne and proclaim such Successor King.
During the expiration of the term of the House of Representatives or the dissolution thereof, the Senate shall act as the National Assembly in acknowledging the matter under paragraph one or in giving an approval under paragraph two.