Thailand's Northeast — known as Isan — is home to more than 22 million people and some of Thailand's most important agricultural land. It is also one of the regions most consistently exposed to drought stress in Southeast Asia.
This article uses real data from GlobMaps' MDI (Multi-Drought Index) pipeline — province-level drought analysis processed from ERA5 reanalysis and MODIS vegetation data — to look at where Isan stands as of May 2026, and what the ENSO signal tells us about risk heading into the second half of the year.
What our latest data shows (May 2026)
GlobMaps MDI pipeline updates monthly on day 8 of each month, using the previous month's ERA5 climate data. The May 2026 update — processed June 9, 2026 — covers all 77 Thai provinces.
Thailand-wide picture:
| Severity | Province count |
|---|---|
| No drought | 52 |
| D0 — Abnormally Dry | 24 |
| D1 — Moderate Drought | 1 |
Source: MDI THA 10e-multi-index-drought.json, generated 2026-06-09. Coverage: 77 Thai provinces.
Top drought-stress provinces (May 2026):
| Province | MDI Score | Severity | Region |
|---|---|---|---|
| Narathiwat | 0.36 | D0 Abnormally Dry | South |
| Samut Sakhon | 0.31 | D0 Abnormally Dry | Central |
| Mukdahan | 0.26 | D0 Abnormally Dry | Northeast (Isan) |
For the Isan region specifically, Mukdahan stands out as the province with measurable drought stress in the May 2026 update. Its MDI score of 0.26 places it in D0 ("Abnormally Dry") territory, with an SPEI-3 of −0.61 — below the −0.5 drought threshold, meaning drier than the 1991–2020 historical average for this province and season. Vegetation tells the same story: Mukdahan's VCI reads 0.54, under the 0.6 vegetation-stress line.
What does D0 mean for farmers?
D0 ("Abnormally Dry") does not yet reach the D1 threshold (SPEI-3 < −0.8) where significant agricultural impacts are documented. However, D0 in May is significant for Isan agriculture for a specific reason: May is the transition month before the Southwest Monsoon fully establishes in the Northeast.
Soil moisture entering the rainy season below baseline means:
- Rice seedling transplantation in early June may face additional water stress
- Reservoirs and small irrigation canals enter the monsoon season at lower-than-average levels
- Pastureland for livestock enters the season more exposed to moisture stress
The ENSO signal: which index you trust changes the story
The drought picture is further shaped by ENSO — but here the headline and the official record disagree. NOAA CPC still carries an El Niño Advisory on a sea-surface-temperature basis, and the legacy Oceanic Niño Index (ONI) reads +0.98 for AMJ (April–June) 2026 — squarely in "El Niño" territory.
But NOAA now treats the Relative ONI (RONI) — which subtracts background ocean warming to isolate the true ENSO signal — as its primary index, and RONI for the same period is +0.47, inside the Neutral range. By the official measure, 2026 is not (yet) an El Niño. The basin-wide label is genuinely contested; the province-level ground signal is not.
Indices as of the NOAA CPC AMJ 2026 update: RONI +0.47 (Neutral — NOAA's primary ENSO index) and legacy ONI +0.98. Source: NOAA CPC.
Why this matters for Isan: Whether or not the basin-wide index tips into El Niño, northeastern Thailand is already carrying below-baseline soil moisture — Mukdahan at D0 in the May 2026 MDI run. An El Niño would raise the odds of a drier second half, but the compound risk to the 2026 growing season is measurable at province level today, ahead of any label.
Looking across Southeast Asia: Vietnam's Kon Tum as a warning
Thailand's drought picture in May 2026 sits at the mild-to-moderate end, and it is worth checking that against a neighbour rather than asserting it in isolation. Kon Tum province, in Vietnam's Central Highlands, recorded MDI 0.141 in the same May 2026 update — below the 0.20 threshold, so no drought class at all.
That contrast is the useful context: the same MDI pipeline that puts Mukdahan at D0 leaves Kon Tum unclassified — the index does capture meaningful variation within the region, and in this case the variation runs the other way from the one a coffee-belt headline would suggest.
Source: MDI VNM 10e-multi-index-drought.json, generated 2026-06-09.
Watching the season
A borderline ENSO signal over already-below-baseline soil moisture is the kind of compound risk that shows up province by province — Mukdahan at D0, Kon Tum unclassified — long before it reaches a regional headline. We will keep following how the Isan picture develops through the 2026 growing season.
More on how we read Southeast Asia's climate at globmaps.com.