This　investigation　explored　the　intensive　characteristics　of　biomass　and　biochar　from　oil　palm　trunk　(OPT)　and　oil　palm　fronds　(OPF)　for　supporting　the　increasing　demand　of　solid　biofuels　in　Thailand.　The　characteristics　of　these　samples　were　also　compared　to　low　grade　sub-bituminous　coal　(LGSBC).　The　results　indicate　that　converting　OPT　and　OPF　to　biochar　not　only　enhanced　the　fuel　ratio　and　atomic　ratios,　but　it　also　improved　the　energy　content.　The　higher　heating　values　(HHV)　of　OPT　and　OPF　biochars　were　26.92　and　28.05　MJ/kg.　The　fuel　ratio,　atomic　ratio　and　HHV　of　biochars　were　better　than　those　of　LGSBC　and　biomass　forms.　Thermal　decomposition　and　combustion　characteristics　of　biomass　and　biochar　from　OPT　and　OPF　were　clearly　different　in　N2　and　air　atmospheres.　The　biomass　and　biochar　from　OPT　and　OPF　had　high　contents　of　alkali　elements,　consequently　their　ashes　had　high　concentrations　of　some　oxides　like　SiO2　and　K2O.　Biomass　and　biochar　ashes　from　OPT　and　OPF　had　low　initial　deformation　temperature　(IDT).　The　IDT　of　OPT　biochar　ash　was　the　lowest　(907　°C),　while　the　IDT　of　ash　from　LGSBC　was　above　1500　°C.　The　slagging　and　fouling　indexes　of　biochars　were　clearly　different　from　the　LGSBC　and　biomass　forms.　Therefore,　biomass　and　biochar　from　OPT　and　OPF　have　potential　for　solid　biofuel　use,　and　they　are　promising　for　further　upgrading　and　applications.　The　user　needs　to　be　concerned　with　ash　related　problems　like　ash　fusion,　slagging,　and　fouling　during　combustion　of　these　solid　biofuels.　©　2022　The　Author(s)