<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2023-11-10</periodOfReport>

    <notSubjectToSection16>false</notSubjectToSection16>

    <issuer>
        <issuerCik>0001108426</issuerCik>
        <issuerName>PNM RESOURCES INC</issuerName>
        <issuerTradingSymbol>PNM</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001083786</rptOwnerCik>
            <rptOwnerName>COLLAWN PATRICIA K</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>CORPORATE HEADQUARTERS</rptOwnerStreet1>
            <rptOwnerStreet2>MS 1275</rptOwnerStreet2>
            <rptOwnerCity>ALBUQUERQUE</rptOwnerCity>
            <rptOwnerState>NM</rptOwnerState>
            <rptOwnerZipCode>87158-1275</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
            <isOfficer>true</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle>CHAIRMAN AND CEO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Stock Shares</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2023-11-10</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>0.00</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <footnoteId id="F2"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>89448.00</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>PNM Common Stock Fund - PNM Resources Executive Savings Plan II</value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The security converts to common stock on a one-for-one basis.</footnote>
        <footnote id="F2">Due to a delay in the receipt of information from the third party administrator, applicable balance information is unavailable. As a result, the number of phantom stock shares acquired by the reporting person cannot be determined at the time of this filing. The reporting person will file an amended Form 4 when the applicable balance information becomes available and will reflect the amount of phantom shares acquired under the PNM Resources, Inc. Executive Savings Plan II through notational dividend reinvestment on the cash dividend payment date of November 10, 2023.</footnote>
        <footnote id="F3">The phantom stock shares were acquired under the PNM Resources, Inc. Executive Savings Plan II, and will settle upon the Reporting Person's retirement or other termination of service.</footnote>
        <footnote id="F4">Reflects the amount of phantom shares based on previous form filed August 29, 2023.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Angela L. Pino, POA for Patricia K. Collawn</signatureName>
        <signatureDate>2023-11-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
