Land measurements in Thailand
Land measurements in Thailand will usually be seen using the established local system.

Thailand is metric so things start in square metres:

4 square metres (2m x 2m) is 1 square Wah (or Talang Wah, as Thai say)

100 Talang Wah is 1 Ngan (This is 400 square metres - ideal for a small to medium house)

1 Rai is 4 Ngan (or 400 Talang Wah or 1,600 square metres) Mostly you'll hear about Rais in Thailand

If you are used to Acres, then 1 Acre = 43,560 square feet or 4840 Square Yards or 4046.8 Square Metres = 2.53 Rai

If you are used to hectares, then 1 Hectare = 10,000 Square Metres = 2.47 Acres = 6.25 Rai.

Quick Conversion Table 1

1 Talang Wah = 4 square meters
1 Ngan = 100 Talang Wah = 400 square meters
1 Rai = 4 Ngaan = 1600 square meters
1 Acre = 4046.8 square meters
1 Hectare = 10,000 square Meters

Quick Conversion Table 2

1 Talang Mett            1 Square Meter                     
1 Talang Wah            4 Square Meters                              
100 Talang Wah        400 Square Meters         1 Ngan                    
400 Talang Wah        1,600 Sqare Meters        4 Ngan       1 Rai          
1,000 Talang Wah     4,000 Square Meters      10 Ngan      2.5 Rai
   
Other Conversions

1 Acre = 43,560 square feet
1 Acre = .4047 hectare
1 Acre = 4047 square meters

1 Centimeter = .3937 inches
1 Centimeter = .032808 feet

1 Foot = 12 inches
1 Foot = 0.3048006 meter

1 Hectare = 10,000 square meters
1 Hectare = 2.471 acres

1 Inch = .0254 meter

1 Meter = 3.280833 feet
1 Meter = 39.37 inches
1 Meter Square = 10.764 square feet

1 Kilometer = 3280.83 feet
1 Kilometer = .62 mile

1 Yard = 36 inches
1 Yard = 3 feet
1 Yard Square = 9 square feet