Start with the local transport model
Bangkok mass transit, a walkable old town, an island dependent on taxis and a rural area requiring a vehicle produce very different budgets. Map recurring journeys first: work, school, groceries, healthcare and airport access. Price the mode that will really be available at those times.
Include access and connection costs
The advertised train, bus or flight fare is only part of a journey. Add travel to the terminal, baggage, seat or booking fees, ferry connections and the cost of arriving late when public transport is limited. A cheaper ticket can be a more expensive door-to-door trip.
Price vehicle ownership honestly
For a car or motorcycle include depreciation or rental, insurance, registration, fuel, parking, tolls, servicing, tyres and accident excess. Confirm licence and coverage before treating a motorcycle as a budget shortcut. Safety equipment is an essential cost.
Use a normal month and a travel month
Keep everyday mobility separate from holidays and visa-related trips. Build a modest disruption allowance for rain, missed connections or surge pricing. Recheck live fares with the operator because route prices and service levels change.
Verify before you act
Rules, timetables, prices and local conditions can change. Use the official source links below for the latest position.