Foreign investors have cut holdings in most emerging Asian government bonds so far this month on expectations that US interest rates will rise in December and that other major central banks will not ease further.
South Korea, India and Thailand have suffered outflows so far in October.
"The global environment for bonds has become less favourable with major central banks contemplating reducing stimuli," said Eugene Leow, interest rate strategist for DBS Bank in Singapore.
The US Federal Reserve is expected to raise interest rates in December, as three months of slower employment growth is not considered enough to stop it from moving.
Also weighing on emerging Asian debt are perceptions that other major central banks
are unlikely to ease further as well as higher oil prices, which have reduced concerns about inflation being too low.
Foreign investors sold a combined net 1.7 trillion won ($1.5 billion) worth of South Korean bonds in the first 10 days of October, preliminary data from the country's Financial Supervisory Service showed.
This follows 663.0 billion won of outflows from bonds in September, with foreigners reducing holdings of maturities of less than one year by 3.4 trillion won, according to separate data from the regulator.
"Short-dated notes are not attractive, given low chances of a rate cut in a near term, although investors extended duration, indicating their sentiment stays bullish," said Shin Dong-su, a fixed-income analyst at Eugene Investment & Securities in Seoul.
South Korea's central bank holds a policy meeting on Thursday and is not expected to lower rates, with rising household debt seen as one hurdle to a cut.
In India, foreign investors booked profits by selling more $600 million worth of domestic bonds this month after buying $1.5 billion of them in September, before a policy meeting on Oct. 4 at which interest rates were cut.
Foreign investors cut Thai bond holdings by 9.2 billion baht ($263.8 million) in the first 10 days of October, following inflows of 15.3 billion baht in September and of 41.1 billion baht in August, according to Reuters calculations based on Thai Bond Market Association data.
Thai markets have fallen this week after a palace statement on Sunday said the health of King Bhumibol Adulyadej, 88, was in an "unstable" condition. Malaysia saw bond outflows in September after three months of inflows.
The central bank revised the outflow figure to 8.4 billion ringgit ($2.0 billion) from an initial 1.4 billion ringgit, according to data on its website seen by Reuters. That was the largest monthly outflow since August last year when the country's markets tumbled on a political crisis swirling around Prime Minister Najib Razak and corruption allegations involving indebted state fund 1Malaysia Development Berhad (1MDB).
Bank Negara Malaysia officials were not available for comments on the revision. Foreign holdings of Indonesian bonds, by contrast, have hardly changed this month. Among Asia's highest yielding bonds, they attracted 16.9 trillion rupiah ($1.3 billion) of inflows in September, nearly double the August level. These inflows came as Bank Indonesia last month delivered its fifth interest rate this year, boosting bond prices. The country also collected 97.2 trillion rupiah in revenue from the first phase of the country's tax amnesty, helping cover the government's fiscal deficit.
Some investors think the falling yuan might prompt some foreign investors to sell Chinese bonds and move into other emerging Asian debt. The renminbi has hit six-year lows this week.
"After CNY depreciation, money has been flowing out of onshore China to the offshore market," said Gordon Ip, investment director at Value Partners in Hong Kong.