Mandarin Oriental Bangkok is offering its grandest suite, the Grand Royal Suite, for 500,000 baht a night.
The five-star hotel is undergoing a big renovation to increase the number of suites to meet high demand, especially during the peak season when guests can find it hard to get a room.
Last year the hotel combined four suites in its Authors' Lounge Wing into a new suite named the Grand Royal Suit.
With six bedrooms over 600 square metres, the Grand Royal Suite occupies the entire first floor of the renowned Authors' Lounge Wing, which used to be the original Oriental Hotel, built in 1876.
"This is one of the biggest suites in the world and also the biggest in Bangkok," said general manager Greg Liddell.
The suite has private elevator access and comprises the master bedroom -- the 315 sq m Royal Suite -- and the adjoining 165 sq m Ambassador Suite with two bedrooms, as well as three separate guest rooms to accommodate family and entourage.
A private separate meeting room offers state-of-the-art security monitoring and communications facilities.
Mr Liddell said many of the world's largest suites can be found in the Middle East. In Thailand, the St. Regis Bangkok arranges larger residential suites for guests upon reservation.
He said Mandarin Oriental Bangkok spent 650 million baht to renovate the Authors' Lounge and Garden wings. It also refurbished its famous restaurant Le Normandie as well as re-arranged guest rooms by combining 58 rooms into 24 suites.
The hotel plans to kick off the next phrase of renovation next month at its River Wing, starting with Lord Jim's restaurant. The eatery is set to reopen in November or December for the high tourism season.
Management plans to renovate all guestrooms in the same wing by combining standard rooms into more suites. All other operations and equipment will be replaced by a new system following this renovation, said Mr Liddell.
"All renovation work is expected to be finished in 2019," he said.
Several more hotel rooms will be added on the banks of the Chao Phraya River in the next few years by luxury operators, but he believes the added players will help cater to the high-end market.
Some new attractions expected along the river include Icon Siam shopping mall, a new art centre by Thailand Creative & Design Center, and a new train line to strengthen tourism in the area.
Some 90% of guests at Mandarin Oriental Bangkok are from the high-end leisure market, higher than the 70% average at other hotels in the Mandarin Oriental Hotel Group.
As of this month, Mandarin Oriental Bangkok recorded an increase in forward bookings of 16-17% year-on-year. Top markets by nationality are the US, UK, Germany, Hong Kong, and Singapore.
"We are seeing more guests from mainland China, the Middle East and Russia," Mr Liddell said.