LAUNCESTON, Australia, Sept 27 (Reuters) - As seaborne coal in Asia trades at, or near, record highs, there are early signs of demand destruction, especially among price-sensitive buyers such as India.

While global seaborne coal volumes have been trending higher in recent months, the market is increasingly becoming split between those importers willing to pay the high prices, and those cutting back on the number of cargoes they are buying.

The total volume of exports of all grades of coal worldwide for September is estimated at 122.8 million tonnes by commodity consultants Kpler, the strongest month since December 2019.

But looking at the breakdown by country for imports in recent months shows the effect of the surge in prices for both thermal coal, used in power plants, and coking coal, used to make steel.

India, the world's second-largest coal importer behind China, is forecast by Kpler to land 13.3 million tonnes in September, which would be the weakest monthly outcome since June 2020, when imports slumped because of the economic hit from lockdowns to combat the coronavirus pandemic.

If the September outcome is in line with Kpler's estimate, then it will be the fourth straight month of declining imports and will put India's September imports some 38% below April's 21.6 million tonnes, which is the highest in 2021.

The breakdown of where India is buying its coal also shows the impact of rising prices, with it taking a greater share from Indonesia, at the expense of Australia.

Indonesian thermal coal trades at a discount to Australian, but also has a lower energy value.

India is on track to import 3.8 million tonnes of all grades of coal from Australia in September, down from 4.79 million in August and 6.4 million in July.

Imports from Indonesia are forecast to rise to 5.09 million tonnes in September, up from 4.3 million in August and 3.34 million in August, according to Kpler.

The demand for Indonesian coal is showing up in prices, with the weekly index for coal with an energy value of 4,200 kilocalories per kilogram (kcal/kg), as assessed by commodity price reporting agency Argus, rising to a fresh record high of $91.28 a tonne in the week to Sept. 24.

This grade has now gained 303% since its 2020 low of $22.63 a tonne, reached in early September of that year.

Benchmark high-grade Australian thermal coal with an energy value of 6,000 kcal/kg, also rose last week, reaching $180.70 a tonne, closing in on its all-time high of $195.25 from July 2008.

The price has gained 290% since its 2020 low of $46.37 a tonne, also in early September.

The high-grade Australian coal is mainly bought by utilities in Japan, South Korea and Taiwan, and isn't a popular grade for Indian importers.

India has been tending to buy Australian 5,500 kcal/kg coal , which ended last week at $108.20 a tonne, up 208% from its 2020 low of $35.06, reached in August of that year.

AUSTRALIAN BAN

This grade used to be mainly bought by China, but the trade came to a halt after Beijing imposed an informal ban on Australian coal in the middle of last year as part of a political dispute.

The effective ban has proved costly for China, which has been forced to buy more Indonesian and Russian coal to meet needs, with Russian cargoes said by traders to be commanding premiums of more than 100% to their Australian equivalents.

China's coal imports are slated to drop in September, with Kpler forecasting seaborne arrivals of 27.4 million tonnes, down from 32.4 million in August and July's 27.65 million.

This is more likely a reflection of lack of available cargoes rather than a cutback due to high prices, especially since Chinese buyers are now competing with India for Indonesian coal.

China's imports from Indonesia are estimated at 15.86 million tonnes in September, down from 19.8 million in August.

If China and India, the top two coal buyers, are importing less, as are some other smaller Asian importers such as Vietnam, then the question becomes who is importing more.

The answer is the wealthier and more developed economies of north Asia, namely Japan, South Korea and Taiwan.

Japan's September imports of all coal grades are expected to reach 16.24 million tonnes, the most since January 2020, while South Korea is on track to import 13.05 million, the highest since October 2019, and Taiwan is expected to bring in 8.02 million tonnes, the most since Kpler started tracking cargoes in January 2017.

The question for the market is how long those countries will pay high prices for coal, or whether they will be able to switch to now cheaper oil-fired generation, or utilise liquefied natural gas (LNG) bought on crude-linked long-term contracts, or even boost the share of nuclear power.

(Editing by Robert Birsel)