Thailand officially ended a year of mourning for its late King Bhumibol Adulyadej on Monday, marking a return to colours for some after a monotone year during which many wore black from head-to-toe out of respect for their revered monarch.

Hundreds of thousands of people thronged Bangkok's historic quarter to bid farewell last week to King Bhumibol, who died in October 2016. His $90 million-dollar funeral, full of pomp and ancient ritual, took place over five days.

His remains were brought to their final resting place within Bangkok's Grand Palace on Sunday. Portraits of the bespectacled late king, who became a father figure for many during a seven-decade reign, were hung across Thailand.

The black-and-white funeral bunting that had hung on the gates of Bangkok's Government House for a year was taken down on Monday and Prime Minister Prayuth Chan-ocha made a televised announcement to mark the official end of the mourning period.

"The government would like to thank officials, both soldiers and civilians ... and the more than 10 million Thais who came to pay respects to the royal body over the past year," Prayuth said.

May Kanokwattana, 29, an office worker, wore bright yellow as she waited at the Siam BTS, a major Bangkok transport interchange.

"I wore black for one year. I needed to show my sorrow. Today is the first day I am wearing a different colour," May told Reuters.

She also wore a pin with the Thai number nine out of respect for King Bhumibol, who was also known as the ninth king of the Chakri Dynasty.

Colours have a profound meaning for Thais. Astrological rules followed by many in the Southeast Asian nation assign a colour to each day of the week.

King Bhumibol was born on a Monday, a day associated with the colour yellow. His only son, new King Maha Vajiralongkorn, was also born on a Monday.

Some people shared charts on social media showing which colours would be considered luckiest to wear.

"For confidence, health and power wear orange. For good support wear pale green," said one chart.

Pattinya Mankongwongcharoen, 49, an accountant wearing a peach-coloured dress, said: "I won't continue wearing black because the mourning period is officially over and to do so would be disrespectful."

Others said they would continue to wear muted colours.

"I'm still grieving. I'll wear black or grey for a few more weeks," said Pimsuda Chatree, 37, a shop owner.