Thailand’s Department of Highways (DOH) is the country’s largest road infrastructure agency. Every DOH highway project requires drainage products that meet Thai Industrial Standards (TIS) and the specific TOR (Terms of Reference) requirements of the project. This guide consolidates what engineers, contractors, and procurement officers need to know before submitting a bid.
TIS standards required by DOH
DOH specifies four mandatory TIS standards for drainage products:
- TIS 128-2560 — Round reinforced concrete (RC) pipes, Ø 0.30–1.50 m, for general highway drainage
- TIS 1164-2559 — Box culverts 0.50 × 0.50 to 1.00 × 1.00 m, for small-to-medium underpasses
- TIS 1165-2559 — Box culverts 1.20 × 1.20 to 2.00 × 2.00 m, for irrigation crossings and large drainage
- TIS 1166-2559 — Special-size box culverts above 2.00 m, for major bridge / expressway projects
All suppliers must hold valid, current TIS certification and produce in factories certified to the relevant standard.
Common sizes used in DOH projects
Most DOH highway projects use these sizes:
- Round pipes Ø 600 / Ø 800 / Ø 1000 mm — standard under-road drainage
- Box culverts 1.00 × 1.00 / 1.50 × 1.50 / 2.00 × 2.00 m — canal crossings, large drainage points
- Round Ø 1500 mm + box 3.00 × 2.00 m — bridge crossings, expressway projects
Engineering specifications
DOH minimum specifications:
- Concrete compressive strength ≥ 240 ksc (kgf/cm²)
- Reinforcement SD40 / SR24 per TIS specification
- Concrete cover to reinforcement ≥ 25 mm
- Testing compressive strength and 3-edge bearing per TIS per production lot
Documentation required for purchase
For government projects, suppliers must provide:
- Valid TIS certificate (stamped factory copy)
- Test report from accredited laboratory (within 6 months)
- Delivery note per shipment
- Certificate of Conformance per project-specific TOR
- ISO 9001 for larger DOH projects
Pricing factors
Concrete pipe pricing for DOH projects depends on:
- Size — Ø 1500 mm costs 4-6× more than Ø 600 mm
- Quantity — best factory pricing starts at 500+ pieces
- Delivery distance — projects within 100 km of Pathum Thani factory: no transport surcharge
- Urgency — rush orders within 7 days: 8-12% overtime premium
Selecting a supplier
Vetting checklist for DOH concrete pipe suppliers:
- Current TIS certification in required categories
- Owned factory (not a broker)
- Verifiable DOH project track record
- In-stock inventory in popular sizes (reduces delay risk)
- Auditable batch-by-batch QC system
Request a quote from Siripong Cement
Siripong Cement manufactures TIS-128, TIS-1164, TIS-1165, and TIS-1166 products at our Pathum Thani factory — 60 years of DOH project experience, full TIS documentation per lot, factory-direct pricing.
Free quote, response within 1 business day — contact us or LINE OA @siripongcement