The exclusive economic zone of Tonga comprises those areas of the sea, seabed, and subsoil that are beyond and adjacent to the territorial sea of Tonga, having as their outer limits a line measured seaward from the baseline described in Sections 5 and 6 of this Act, every point of which line is distant 200 nautical miles from the nearest point of the baseline.
(2) Notwithstanding subsection (1) of this section, where/-
(a) Any part of the median line between Tonga and any other country is less than 200 nautical miles from the nearest part of the baseline of the territorial sea of Tonga; and
(b) No other outer limit of the exclusive economic zone is for the time being determined by agreement
with a neighboring country or by an Order-in-Council made under subsection (3) of this section -
that part of the median line shall be an outer limit of the zone.
(3) For the purposes of implementing any international agreement, or the arbitral award of any international body, or the judgement of any international Court, or for any other purpose in accordance with international law, the King may from time to time, by Order-in Council, declare that the exclusive economic zone shall not extend to any specified area of the sea, seabed, or subsoil, that would otherwise be included within the exclusive economic zone by virtue of this section
https://www.un.org/depts/los/LEGISLATIONANDTREATIES/PDFFILES/TON_1989_Act.pdf
The Exclusive Economic Zone for Tonga was extracted from the Global Marine Regions platform. Tonga has not formally deposited with UNDOALOS their 200M.