Every waterfront plot carries some water risk. The question is how much, and what can be done about it. What can actually be checked before you commit.
No waterfront plot in Thailand is entirely free of water risk. The useful question is not "does it flood" but "how often, how deep, and what can be done about it".
First and most important. A riverside plot in March and the same plot in October are not the same property.
If you can only see it once, go late in the wet season — September to November in the central plains, when levels are at their annual highest.
Long-standing neighbours are the most direct source there is. Ask how high the water has reached, which year was worst, and how many days it stayed up.
The question that gets a good answer is "where did the water reach on your house in 2011", because everyone remembers that year.
Staining on walls, fences and existing house posts records the high-water line more reliably than anyone's memory. Look for the change in colour on rendered walls, and the height at which trees have put out surface roots.
Measure how far the land sits above or below the road at the front. If it is below, it will need filling, and that is a cost with a number attached that belongs in the offer.
Fill costs depend on haulage distance and volume. Get a real quotation rather than an estimate before committing.
On a river with any current, the bank erodes a little every year. Look for existing bank protection, what condition it is in, and who pays to maintain it.
Building new bank protection is expensive and may require permission.
Waterfront land has a problem ordinary land does not: the boundary on the water side can move, through erosion or accretion.
The Land Office holds the current boundary record. Check whether the area on the deed still matches the ground. A large discrepancy may mean a fresh survey.
Land fronting a public waterway also often has a strip of state land between the plot and the water, which can be used but is not owned.
Anything built out over a waterway needs permission from the Marine Department. Jetties, bridges and riverside pavilions all fall under this.
Existing structures built without permission can be ordered removed. Check whether the permits exist before you buy, not after.
Flooding is not automatically a reason to refuse a waterfront plot. Plenty of land floods for a few days a year and is handled by building at a raised level. What goes wrong is buying without knowing what has to be dealt with, then discovering the real cost afterwards.
Waterfront land carries building restrictions ordinary land does not: setbacks from the water, Marine Department permits, and zoning. What to establish before paying for a design.
Two riverside plots of identical area can be worth very different amounts, because of how much of each touches the water. Why that is, and how to compare them properly.
A single plot carries at least two prices. The Land Department's assessed value sets the taxes; the market price is what it changes hands for. Knowing which is which keeps the sums right.
