BANGKOK (Reuters) - Thai lawmakers have been asked not to leave the country next week, the head of parliament said on Tuesday, as a much-touted December date for Crown Prince Maha Vajiralongkorn to ascend the throne draws near.

The death of King Bhumibol Adulyadej on Oct. 13 at the age of 88 has left the Southeast Asian nation of 67 million people without a monarch, but Prime Minister Prayuth Chan-ocha has made it clear that the king's only son and appointed heir, Prince Vajiralongkorn, will inherit the throne.

Thailand is making preparations for the prince to ascend the throne on Dec. 1, Reuters reported in October.

Pornpetch Wichitcholchai, head of the National Legislative Assembly, said lawmakers had been asked not to take leave between Nov. 28 and Dec. 2 and not to travel abroad or outside of the capital Bangkok over an upcoming long weekend holiday.

"December 3 to December 5 are holidays and the government might have urgent legislation to raise or a special session might be called," Pornpetch told Reuters.

Pornpetch said that the assembly had not yet been ordered by the government to enact Article 23 of the constitution, which says that parliament will convene and invite the heir to the throne to become king and "proclaim such heir king".

Parliament needs a quorum in order to proclaim the new monarch.

Prayuth said last month that the prince had asked to delay his ascension to the throne while he mourns his father.

Regardless of when the prince ascends the throne, a formal coronation can only take place following the late king's cremation next year.

(Reporting by Amy Sawitta Lefevre and Panarat Thempgumpanat; Editing by Nick Macfie)