June 19 (Reuters) - Asian bonds attracted their largest monthly foreign inflows in a year in May, helped by a cooling inflation trend in the United States and an improving economic outlook in Asia.

Overseas investors purchased about $9.5 billion worth of bonds in Indonesia, Malaysia, India, South Korea and Thailand last month, marking their largest net buying since May 2023, data from regulatory authorities and bond market associations showed.

"Softening inflation numbers in the U.S. helped improve investor sentiment, particularly towards bonds," said Khoon Goh, head of Asia research at ANZ.

Data released last week showed producer prices in the United States unexpectedly fell in May and consumer prices remained unchanged for the first time in nearly two years, fuelling investor optimism for a potential Federal Reserve interest rate cut in September.

Indonesian bonds attracted $5.8 billion in foreign inflows last month after three consecutive months of outflows, driven largely by purchases of Bank Indonesia rupiah securities (SRBI).

Eugene Leow, a senior rates strategist at DBS Bank, suggested that investors might have engaged in opportunistic buying following the surge in Indonesian government bond yields in late April.

"As U.S. rates fell in May, there was probably more impetus for foreign investors to come in," the strategist said.

Malaysian bonds received $1.16 billion, the largest monthly foreign inflow since July 2023, buoyed by data showing upbeat economic performance in the first quarter of 2024.

Indian and South Korean bonds received about $1.1 billion each on a net basis, while Thai bonds got a net $423 million.

Analysts have indicated that an improved growth outlook in Asia could further bolster portfolio inflows later this year.

Recent data showed South Korea's exports climbed 11.7% year-on-year in May to reach a 22-month high. Indonesia's exports rose 2.86% annually last month and beat market expectations, while Taiwan reported a seventh consecutive monthly increase in exports.

"The recent trend in Asia's growth has been encouraging for portfolio flows. Growth in Asia will remain strong due to the ongoing export recovery in several economies," ANZ's Goh said.

(Reporting by Gaurav Dogra and Patturaja Murugaboopathy in Bengaluru; Editing by Subhranshu Sahu)