I was correct about the palace having been dismantled. In her book, Salote Queen of Paradise, Margaret Hixon says that Burns Philps ‘salvaged the once magnificent boards and carted them away.’
She also quotes from, as she calls her, ‘English’ writer Mary Stuart Boyd who it turns out was actually Scots. She was in Ha’apai and visited the palace. Margaret Hixon gives a small quote but I managed to find all of what she wrote.
"An ornamental paling, inside which flourished a row of gorgeous croton-bushes, enclosed the king’s palace. There was no path across the unmown grass; and the large, yellow-bodied spiders of the latitude, acting in agreeable conformity with the statement of Solomon, had taken hold with their hands and suspended their webs from every angle of the white-painted verandah posts. On close inspection the residence, though but three years old, showed signs of dilapidation. There was no one in charge: an ornate door, several of its coloured-glass panels shattered, opened at a touch.
Within, the apartments were lofty and well-proportioned. The wall-paper in the dining-room was elaborately gilt, the carpet a sturdy brussels. Further, it held a commonplace modern sideboard, and a side-cabinet on whose top rested as hideous a pair of crystal-fringed girandoles as ever vile taste of trader exported.
Other furniture there was none. Ascending a carpeted stair, the neglected condition of whose brass rods would have made a conscientious housemaid weep, we came upon the royal bed-chamber. Here was the same incongruity displayed. The rusty iron frame of a huge tent bedstead occupied the centre of the floor. A couple of mattresses lay in a corner, and thrown carelessly upon them was a lace edged canopy of white sateen, evidently designed for the adornment of the great skeleton bed. That was all. In a third room, probably meant to serve as audience-chamber, a spasmodic attempt at thrift had partly rolled up the carpet, leaving exposed an under-lining of felt paper—a Northern petty economy which one smiled to encounter among the idyllic isles of the South Pacific. Perched on the roof was a little, many-windowed tower. In point of temperature, even so early as 10 A.M., it would have served as a practicable oven, while at noon it were safe to prophesy that a joint laid therein would have been certain to be overdone. Doubtless the same adviser who had counselled the purchase of a canopied iron bedstead for a monarch whose soul craves nought more lofty than a sleeping-mat, had deemed it advisable that a smoking-room in that tropical climate should be enclosed with heat-attracting glass. It was a relief to get outside even into the damp heat of the hurricane season, a heat which rendered every movement an exertion."
It seems to be a tradition in Tonga to allow palaces to fall into disrepair. LOL.
I note there was wallpaper in the palace and that would have been a good idea in the Nuku'alofa palace to hide the wood panels.